Crystallographic data were recorded from crystals of photosynthetic reaction center (PRC) that were photolyzed just prior to flash-cooling. Under these conditions, PRC can form a charge-separated state with similar kinetics at room temperature. PRC crystals that are flash-cooled without photolysis are inactive. The resulting structural analysis showed a significant twisting of the ubiquinone moiety. The observed 5 E translation and 180 degree rotation appears to be necessary for activating PRC by forming the proper charge-separated state.